Wavelength Division Multiplexing (WDM) systems utilize multiple channel signal wavelengths to carry multiple signals in an optical fiber. Dense WDM (DWDM) and Coarse WDM (CWDM) and other systems which utilize WDM will be collectively referred to as WDM systems. Optical communication systems (OCS) typically utilize optical amplifiers, such as erbium-doped fiber amplifiers (EDFA), in each section of fiber to amplify optical signals in the optical domain. However it is important to control of the gain of the EDFA. Most EDFA deployed in most OCS can control the gain of an EDFA using a control loop. However these systems typically only control the average gain of the EDFA. Changes in the input spectrum fed to the amplifier (spectral occupancy and power profile) will affect the per channel gain experienced. As a consequence, typical EDFA control loops cannot compensate for the effects of changing the spectral occupancy (adding or deleting a wavelength channel).
Spectral Hole Burning (SHB) is a known effect that causes fast gain changes to the output of an EDFA due to changes in the spectral occupancy. Undesired dynamic and static perturbations resulting from SHB have in the past been compensated by the photonic layer. However conventional systems use costly equipment to control the gain changes resulting from changes in the spectral occupancy for systems which utilize EDFAs. Furthermore these systems take time to adjust for changes in the spectral occupancy, increasing the amount of time needed to add or delete channels.
There exists a need for an improved OCS which can more quickly adjust the spectral occupancy for an EDFA based OCS.